The present invention relates to a modified locking structure and, more particularly, to a modified locking structure installed in a retractable draw bar of a travelling case to facilitate the protraction/retraction and the positioning of the retractable draw bar. The retractable draw bar can be pulled upwards or pressed downwards so as to achieve smooth operation. Moreover, convenient assembly of the retractable draw bar can be achieved.
For a travelling case with rollers installed at the bottom thereof, there is a retractable draw bar allocated to facilitate the protraction/retraction of a draw handle so that the draw handle can be gripped conveniently when used and occupies no space when not used. Moreover, to let the retractable draw bar be positioned at a proper position when protracted, there is a locking structure installed between a first joint tube and a second joint tube to control the retractile state of each joint tube.
With the retractable draw bar of a commercial travelling case as an example, the locking structure installed at a first joint tube has a first positioning element. A first positioning part is installed in the first positioning element to be pushed by a transverse spring so as to be secured in a click hole of a second joint tube and joined with an L-shaped plate. The L-shaped plate is drawn by a cord connected to the push mechanism of a draw handle so that the L-shaped plate can be pulled upwards via the cord to let the first positioning part be retracted into the click hole. The first joint tube can thus be pushed into the second joint tube. The first positioning part is retracted by the leverage generated by the L-shaped plate. Because the path of lever motion is circular but not rectilinear, the transverse locomotion of the first positioning part is not smooth so that obstruction will easily arise. Moreover, the L-shaped plate can only apply to upward-pull type retractable draw bars and can not apply to downward-push type retractable draw bars.
With the retractable draw bar of another commercial travelling case as another example, the locking structure of a first joint tube has a tube seat. A transverse allocation hole with a bead allocated therein is installed in the tube seat. A movable plate pushed upwards by a spring is longitudinally inserted in the tube seat. The top of the movable plate is drawn by a cord. The bottom of the movable plate has a circular slide part facing the bead. When the first joint tube is pulled out, the bead will be pushed by the slide part to be secured in a click hole of a second joint tube. When the cord is pulled upwards to pull the movable plate upwards, the bead will be freed and pressed by the first joint tube so that the bead will leave the click hole. However, when the movable plate is pulled upwards by the cord, there is no spring or other force to push the bead. The bead is only freed and rolls off. Therefore, it is not certain whether the bead will leave the click hole. It is possible that the bead is still jammed in the click hole so that the protraction/retraction of the draw bar will be blocked. Furthermore, the draw bar will not be steadily positioned when pulled upwards. Similar to the above example, the L-shaped plate can only apply to upward-pull type retractable draw bars and can not apply to downward-push type retractable draw bars.
One object of the present invention is to provide a modified locking structure of a retractable draw bar, which not only applies to upward-pull type retractable draw bars, but also applies to downward-press type retractable draw bars. Moreover, the locking state of the retractable draw bar can be released timely.
Another object of the present invention is to provide a modified locking structure of a retractable draw bar, which can facilitate the protraction/retraction of the retractable draw bar and can steadily position the retractable draw bar when the retractable draw bar is pulled to a predetermined position.
To achieve the above objects, a locking mechanism comprising a fixed assembly, a movable assembly, and a click button is installed at the bottom opening of a first joint tube. The movable assembly has a longitudinally long guide hole to let a guide block and a pin bar of the fixed assembly penetrate through transversely so that the movable assembly can steadily move upwards or downwards with respect to the fixed assembly. The click button matched to a resilient element is allocated in a transverse allocation tank of the fixed assembly and protrudes in the long guide hole to be secured in a click hole of a second joint tube timely. A wedged guide groove and a wedged guide block both having an upper bevel and a lower bevel are installed at corresponding positions of the movable assembly and the click button, respectively. When the movable assembly is pulled upwards or pressed downwards, the click button can thus be pushed sideward and retracted transversely from the click hole.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawings, in which: